Re: [Xen-devel] [PATCH 06/11] ARM: simplify page type handling

[Stefano Stabellini]

On Wed, 21 Jun 2017, Jan Beulich wrote:
> There's no need to have anything here on ARM other than the distinction
> between writable and non-writable pages (and even that could likely be
> eliminated, but with a more intrusive change). Limit type to a single
> bit and drop pinned and validated flags altogether.
> 
> Signed-off-by: Jan Beulich 

Reviewed-by: Stefano Stabellini 


> ---
> Note: Compile tested only.
> 
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -1113,8 +1113,7 @@ void share_xen_page_with_guest(struct pa
>  spin_lock(>page_alloc_lock);
>  
>  /* The incremented type count pins as writable or read-only. */
> -page->u.inuse.type_info  = (readonly ? PGT_none : PGT_writable_page);
> -page->u.inuse.type_info |= PGT_validated | 1;
> +page->u.inuse.type_info = (readonly ? PGT_none : PGT_writable_page) | 1;
>  
>  page_set_owner(page, d);
>  smp_wmb(); /* install valid domain ptr before updating refcnt. */
> --- a/xen/common/memory.c
> +++ b/xen/common/memory.c
> @@ -354,8 +354,10 @@ int guest_remove_page(struct domain *d,
>  
>  rc = guest_physmap_remove_page(d, _gfn(gmfn), mfn, 0);
>  
> +#ifdef _PGT_pinned
>  if ( !rc && test_and_clear_bit(_PGT_pinned, >u.inuse.type_info) )
>  put_page_and_type(page);
> +#endif
>  
>  /*
>   * With the lack of an IOMMU on some platforms, domains with DMA-capable
> --- a/xen/include/asm-arm/mm.h
> +++ b/xen/include/asm-arm/mm.h
> @@ -77,20 +77,12 @@ struct page_info
>  #define PG_shift(idx)   (BITS_PER_LONG - (idx))
>  #define PG_mask(x, idx) (x ## UL << PG_shift(idx))
>  
> -#define PGT_none  PG_mask(0, 4)  /* no special uses of this page   */
> -#define PGT_writable_page PG_mask(7, 4)  /* has writable mappings? */
> -#define PGT_type_mask PG_mask(15, 4) /* Bits 28-31 or 60-63.   */
> -
> - /* Owning guest has pinned this page to its current type? */
> -#define _PGT_pinned   PG_shift(5)
> -#define PGT_pinnedPG_mask(1, 5)
> -
> - /* Has this page been validated for use as its current type? */
> -#define _PGT_validatedPG_shift(6)
> -#define PGT_validated PG_mask(1, 6)
> +#define PGT_none  PG_mask(0, 1)  /* no special uses of this page   */
> +#define PGT_writable_page PG_mask(1, 1)  /* has writable mappings? */
> +#define PGT_type_mask PG_mask(1, 1)  /* Bits 31 or 63. */
>  
>   /* Count of uses of this frame as its current type. */
> -#define PGT_count_width   PG_shift(9)
> +#define PGT_count_width   PG_shift(2)
>  #define PGT_count_mask((1UL<  
>   /* Cleared when the owning guest 'frees' this page. */
> 
> 
> 
> 

___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

[Xen-devel] [PATCH 06/11] ARM: simplify page type handling

[Jan Beulich]

There's no need to have anything here on ARM other than the distinction
between writable and non-writable pages (and even that could likely be
eliminated, but with a more intrusive change). Limit type to a single
bit and drop pinned and validated flags altogether.

Signed-off-by: Jan Beulich 
---
Note: Compile tested only.

--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -1113,8 +1113,7 @@ void share_xen_page_with_guest(struct pa
 spin_lock(>page_alloc_lock);
 
 /* The incremented type count pins as writable or read-only. */
-page->u.inuse.type_info  = (readonly ? PGT_none : PGT_writable_page);
-page->u.inuse.type_info |= PGT_validated | 1;
+page->u.inuse.type_info = (readonly ? PGT_none : PGT_writable_page) | 1;
 
 page_set_owner(page, d);
 smp_wmb(); /* install valid domain ptr before updating refcnt. */
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -354,8 +354,10 @@ int guest_remove_page(struct domain *d,
 
 rc = guest_physmap_remove_page(d, _gfn(gmfn), mfn, 0);
 
+#ifdef _PGT_pinned
 if ( !rc && test_and_clear_bit(_PGT_pinned, >u.inuse.type_info) )
 put_page_and_type(page);
+#endif
 
 /*
  * With the lack of an IOMMU on some platforms, domains with DMA-capable
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -77,20 +77,12 @@ struct page_info
 #define PG_shift(idx)   (BITS_PER_LONG - (idx))
 #define PG_mask(x, idx) (x ## UL << PG_shift(idx))
 
-#define PGT_none  PG_mask(0, 4)  /* no special uses of this page   */
-#define PGT_writable_page PG_mask(7, 4)  /* has writable mappings? */
-#define PGT_type_mask PG_mask(15, 4) /* Bits 28-31 or 60-63.   */
-
- /* Owning guest has pinned this page to its current type? */
-#define _PGT_pinned   PG_shift(5)
-#define PGT_pinnedPG_mask(1, 5)
-
- /* Has this page been validated for use as its current type? */
-#define _PGT_validatedPG_shift(6)
-#define PGT_validated PG_mask(1, 6)
+#define PGT_none  PG_mask(0, 1)  /* no special uses of this page   */
+#define PGT_writable_page PG_mask(1, 1)  /* has writable mappings? */
+#define PGT_type_mask PG_mask(1, 1)  /* Bits 31 or 63. */
 
  /* Count of uses of this frame as its current type. */
-#define PGT_count_width   PG_shift(9)
+#define PGT_count_width   PG_shift(2)
 #define PGT_count_mask((1UL<
---
Note: Compile tested only.

--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -1113,8 +1113,7 @@ void share_xen_page_with_guest(struct pa
 spin_lock(>page_alloc_lock);
 
 /* The incremented type count pins as writable or read-only. */
-page->u.inuse.type_info  = (readonly ? PGT_none : PGT_writable_page);
-page->u.inuse.type_info |= PGT_validated | 1;
+page->u.inuse.type_info = (readonly ? PGT_none : PGT_writable_page) | 1;
 
 page_set_owner(page, d);
 smp_wmb(); /* install valid domain ptr before updating refcnt. */
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -354,8 +354,10 @@ int guest_remove_page(struct domain *d,
 
 rc = guest_physmap_remove_page(d, _gfn(gmfn), mfn, 0);
 
+#ifdef _PGT_pinned
 if ( !rc && test_and_clear_bit(_PGT_pinned, >u.inuse.type_info) )
 put_page_and_type(page);
+#endif
 
 /*
  * With the lack of an IOMMU on some platforms, domains with DMA-capable
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -77,20 +77,12 @@ struct page_info
 #define PG_shift(idx)   (BITS_PER_LONG - (idx))
 #define PG_mask(x, idx) (x ## UL << PG_shift(idx))
 
-#define PGT_none  PG_mask(0, 4)  /* no special uses of this page   */
-#define PGT_writable_page PG_mask(7, 4)  /* has writable mappings? */
-#define PGT_type_mask PG_mask(15, 4) /* Bits 28-31 or 60-63.   */
-
- /* Owning guest has pinned this page to its current type? */
-#define _PGT_pinned   PG_shift(5)
-#define PGT_pinnedPG_mask(1, 5)
-
- /* Has this page been validated for use as its current type? */
-#define _PGT_validatedPG_shift(6)
-#define PGT_validated PG_mask(1, 6)
+#define PGT_none  PG_mask(0, 1)  /* no special uses of this page   */
+#define PGT_writable_page PG_mask(1, 1)  /* has writable mappings? */
+#define PGT_type_mask PG_mask(1, 1)  /* Bits 31 or 63. */
 
  /* Count of uses of this frame as its current type. */
-#define PGT_count_width   PG_shift(9)
+#define PGT_count_width   PG_shift(2)
 #define PGT_count_mask((1UL<